According to Duff and Stewart (1933) the pigment is water- 

 soluble. If ethyl alcohol is added to an agar slant the pigment 

 diffuses out into the solution (Arkwright 1912, Duff and Stewart 1933 )• 

 Arkwright (1912) demonstrated from his studies that when dried the 

 pi,gment was not soluble in absolute alcohol. 



An experiment performed by Williamson (1928) showed that the 

 coloration produced by B. salmonicida is a true pigment — both active 

 growth and free o^gen being necessary — and not an oxidation product. 

 Three cultures (Hos. 1, 2, and 3) of the organism were put up at the 

 same time on f ish-extract-agar slopes. All vrere incubated at room 

 temperature. No. 1 aerobically, Nos. 2 and 3 anaerobically, in Buchner 

 tubes. In 4 days pigment began to appear in No. 1, and all were kept for 

 14 days, when there was intense pigmentation in No. 1 and no trace of 

 pigment in No. 2 or Ko. 3* Then No. 2 was removed from the Buchner tube 

 and left exposed to air, while No. 3 on removal from the Buchner tube, 

 was sterilized by exposure to 60° C. for 1 hour. On the same day a 

 fresh culture. No. 4, vras made and kept under aerobic conditions. Four 

 daj'"s later Nos. 2 and 4 showed commencing pigment production, and in 6 

 days this was marked,* No. 3 remained unpigmented. 



Salt stability 



B. salmonicida has been found to be auto-agglutinable in salt 

 solutions of as low concentration as 0.1 percent sodium chloride 

 (Arkvrt-ight 1912, miliarason 1928). However, Duff (1939), while dealing 

 ■with special phases of the organism, consistently, obtained stable 

 suspensions of all pure S- (smooth) and G-phase cultures in 0.8 percent 

 sodium chloride (see below). He also found that R-phase (rough) cultures, 

 w-hile readily auto-agglutinable in salines down to 0.2 percent, formed 

 satisfactorily stable suspensions in 0.05 percent sodium chloride (see 

 belov;). In general it may be said that B. salmonicida is auto- 

 agglutinable in salt solutions of very lovr concentration. 



Emulsions in distilled water are unstable according to Williamson 

 (1923). Arkvirright (1912) did find, however, that an emulsion remained 

 uniform for 24 hours. 



Biochemical Reactions 



Gelatin 



The findings of various vrorkers on the reaction of B. salmonicid a 

 to gelatin are quite variable. Table 2 lists the results of various 

 authorities vath respect to grovrbh, liquefaction, and pigment production. 



13 



